The present invention is an improvement of the rotatable wheel assembly structures, i.e., the wheel calculators, disclosed and claimed in prior U.S. Pat. No. 4,323,609. As there pointed out, wheel calculators are well known handy informational tools that can be adapted to furnish a variety of data in an easily understandable format. Since the utility of wheel calculators as an informational tool helps assure their preservation, wheel calculators are also effectively used for promotional purposes such as advertising.
Generally speaking, a wheel calculator of one type of construction described in the said prior patent includes a front cover having a window opening provided therein, a back cover usually integral with and folded over against the front cover (although the two covers could be separate elements merely laid over each other), and a rotatable wheel member sandwiched therebetween and bearing indicia selectively viewable through the window opening. One of the covers, usually the back cover, and the wheel member each has a hole therein, the holes being identical in shape and size and in the assembled structure being axially aligned with each other, and a patch of adhesive is located at the outside face of the back cover, the adhesive overlying the hole in the back cover and through the two holes adhesively engaging the inside face of the front cover. Thus, the adhesive, once it is completely set, forms a grommetless axle or pivot about which the wheel member can turn.
In a somewhat simpler alternative construction described in the prior patent, the back cover does not have a hole therein but has an adhesive patch or layer affixed to its inside face over a region the same in size and shape as the hole in the wheel member. In this variant, when the structure is assembled with the hole in the wheel member axially aligned with the adhesive patch or layer, the adhesive engages the inside face of the front cover (or a corresponding application of adhesive affixed to the inside face of the front cover) through the hole in the wheel member and thereby forms the desired grommetless axle or pivot for the wheel member. In this type of construction too, the two covers could be separate elements from each other.
For more specific details of the various forms of wheel calculators, as well as of the different types of materials of which they can be made and of the different methods by which they can be made, reference should be had to the aforesaid prior patent.
In a mass production environment, however, it has been found difficult, especially in the case of the type of construction where neither cover has a hole in it, to provide an adhesive layer or patch on the inside face of one or the other of the two covers which conforms precisely in both size and location to the hole in the wheel member. The problem which has then been encountered is that if the adhesive layer is either larger than or not in exact registry with the hole, the adhesive comes into contact with the edge of the hole or the surface region of the wheel member bounding the hole, with the result that it binds the wheel member and precludes it from turning. While the binding problem can be avoided by making the adhesive application sufficiently smaller in diameter than the hole in the wheel member so as to ensure that the peripheral edge of the adhesive is recessed inwardly from the edge of the hole, it is then found that the pivot or axle structure is necessarily considerably smaller than the hole, which results in the wheel member being loose and jiggling, which in turn may cause the indicia on the wheel member occasionally to be not properly aligned with and hence not clearly viewable through the window opening in the front cover. The wheel calculator then loses some of its attractiveness for both the advertiser and the user.